LONDON, March 18 (Reuters) - Britain has suspended bilateral military co-operation with Russia that is not subject to treaty obligations, Foreign Secretary William Hague said on Tuesday, responding to Russian moves to annex Ukraine's Crimea region.

Hague said this included cancelling a planned French-Russian-UK-United States naval exercise and suspending a proposed Royal Navy ship visit to St Petersburg.

Hague also said Britain would be pushing for the strongest possible package of further sanctions against Russia that could be agreed among European leaders when the European Union council meets later this week.